1. Field of the Invention
The present invention relates to an imaging apparatus, and, more particularly, to an apparatus and method for performing mechanical printhead alignment in an imaging apparatus.
2. Description of the Related Art
An imaging apparatus, in the form of an ink jet printer, forms an image on a print medium by ejecting ink from a plurality of ink jetting nozzles of an ink jet printhead to form a pattern of ink dots on the print medium. Such an ink jet printer typically includes a reciprocating printhead carrier that transports one or more ink jet printheads across the print medium along a bi-directional scanning path defining a print zone of the printer.
When printing with multiple color printheads or a color and photo printhead, the printheads must be aligned in both the scan and media feed directions for optimal print quality. In particular, printhead alignment in the media feed direction may be difficult to achieve. Manufacturing variation between any two given printheads often results in unacceptable variations in printhead relative location in the media feed direction. Some adjustment of the printheads in the media feed direction can be performed by the imaging data formatter of the imaging apparatus. For example, in an imaging apparatus using staggered printheads each having a nozzle spacing of 1/600 inch, the formatter can effectively align the printheads in increments of one nozzle spacing. That is, knowing the location of the respective swaths, the formatter can adjust which nozzles are used, turning off those nozzles which are overlapping or by alternating use of the overlapped nozzles between the two printheads.
A finer adjustment of 1/1200 inch or less is required for optimum print quality, since the maximum distance that drops of like size can be misaligned in such an imaging apparatus is 1/1200 inch. However, such an adjustment cannot be performed by the formatter, since the nozzle misalignment is less than the nozzle spacing, e.g., less than 1/600 inch in the example given, and hence, a physical movement of a printhead along the media feed direction is required, as opposed to the logical movement performed by the formatter. If a printer does not fire the print heads simultaneously, then the formatter and paper feed rate adjustments can be used to compensate for y-axis (media feed direction) alignment. In the case where the print heads are fired simultaneously, such a physical movement of the printhead is needed.
What is needed in the art is an apparatus and method for performing mechanical printhead alignment in an imaging apparatus along the media feed direction.